The proposed investigation is a continuation of work carried out by the principal investigator on nervous pathways involved in somesthesis. The aim is to analyze the cellular and synaptic organization of the postcentral gyrus with a variety of light and electron microscopic techniques. The work is being extended to study the interactions of nerve cells and afferent axons during development of the cerebral cortex and to determine to what extent morphological plasticity may occur after experimental manipulations or the afferent pathways to the same somatic sensory cortex. BIBLIOGRAPHIC REFERENCES: Jones, E.G., and Burton, H. 1976 A projection from the medial pulvinar to the amygdala in primates. Brain Research 104: 142-147. Wise, S.P. and Jones, E.G. 1976 Transneuronal or retrograde transport of 3H adenosine in the rat somatic sensory system. Brain Research 107: 127-131.